High-wattage lamps are commonly used in commercial and residential lighting. Recessed lighting fixtures are popular in these applications. However, a continuing problem in recessed lighting is that certain high-wattage lamps cannot be used, because they generate so much heat in operation that they present a fire hazard.
A recessed lighting fixture has a housing that is installed in a recess between ceiling joists or other ceiling members. FIG. 1A is a perspective view of a lighting fixture housing 100, which comprises arms 102, 104 that are secured to the ceiling members, a junction box 106 for receiving conduit and wiring, and a downward facing, open housing or box 108 that encloses and protects other elements of the fixture. The open box accepts any of several kinds of trims (not shown) through hole 110. The trim is secured within the box using screws or locking metal tabs or springs that engage complementary slots. A trim comprises a lamp socket, wiring that is coupled to the wiring of the box 108, and cosmetic elements such as a rim or gimbaled eyeball mechanism. The lamp socket receives a lamp.
There are dozens of different trim types and styles, each of which is compatible with the housing 100 or other standard housings. The housing 100 may be, for example, one of the housings offered under the brand name LiteBox by Prescolite, Inc. of San Leandro, Calif.
The type of lamp that can be used in a recessed fixture, however, is limited by fire codes and other safety concerns. Lamps that draw high current or operate at high wattage may become so hot in operation that they ignite the ceiling members or surrounding ceiling insulation. The lamps are cooled only by passive dissipation of heat from the metal housing or trim to the ceiling airspace and ceiling members. Thus, currently, the maximum allowable wattage ratings of such fixtures are restricted by the ability of the housing to carry out passive heat transfer to the ambient environment. This problem becomes acute when the ceiling is packed with flammable insulation.
For this reason, most recessed lighting housings are rated either for insulation contact ("IC-rated"), or may not be used in direct contact with insulation ("non IC-rated").
The allowable housing surface temperature differs for IC and non-IC-rated fixtures, according to the National Electrical Code (NEC). IC-rated fixture housing temperatures may reach only 90.degree. C. at any point that touches potentially flammable material. The housings of non-IC fixtures may reach 150.degree. C., but points of support and junction boxes may not exceed 90.degree. C.
However, there is a continuing need and desire to use high-wattage lamps in recessed fixtures. For example, high-wattage lamps are useful when large areas are lit, when ceilings are high, and in specialty settings such as retail store lighting. Accordingly, there is a need for a way to cool a lamp, a housing, a trim, or a fixture to enable higher wattage lamps to be used in recessed lighting. Prior fixtures that do not have a thermal protector generally can not comply with NEC requirements when a high-wattage lamp is used.
The construction industry tends to favor standards in the construction of electrical products. Contractors and electricians find it convenient to repeatedly use housings, trims, and other products that have a familiar shape, size, and mechanical constructions. Thus, there is a need for an apparatus that enables a high-wattage lamp to be used in an existing recessed lighting housing without modification by the end user.
Electricians, contractors, and other end users also appreciate the ability to change the configuration of a light fixture. For example, long after a light fixture is installed in a permanent recessed ceiling location, the purpose of the room that is illuminated by the fixture may change. Remodeling may occur. The end user of the fixture may wish to change the type or brightness of the lamp used in the fixture. Thus, there is a need for an apparatus that enables a high-wattage lamp to be used in a recessed lighting fixture, and also enables the type or brightness of the lamp to be easily changed.
Certain work of others shows a fan in combination with a lamp, as exemplified by U.S. Pat. No. 5,664,872 (Spearman et al.); U.S. Pat. No. 5,458,505 (Prager); U.S. Pat. No. 5,021,932 (Ivey); and U.S. Pat. No. 5,626,416 (Romano et al.). However, this other work does not overcome the above-noted problems.
Spearman describes a combined fan-lamp assembly in which the fan is intended to ventilate room air and not to cool the lamp. The lamp of Spearman is enclosed in a sealed compartment that does not receive airflow from the fan. The fan exhaust is directed upward into a duct or the ceiling area and not back into the room where it can be cooled. Spearman does not disclose use of thermal protection.
Prager describes a lamp socket that includes a fan for cooling a bulb and a second socket that receives the bulb. Prager does not disclose use of thermal protection. Prager does not disclose a trim that encloses a cooling volume separate from a volume of a housing into which the trim is inserted. Prager does not disclose how to exhaust warmed air back into the ambient environment so that it can be cooled. Prager lacks a thermal protector and therefore is not practical for use as recessed lighting in jurisdictions subject to the NEC.
Romano et al. discloses a stage lighting fixture with a 2000-watt xenon lamp. Romano et al. does not disclose a trim that encloses a cooling volume separate from a volume of a housing into which the trim is inserted.
Ivey describes a safety device for a combined fan-light unit. Ivey essentially discloses a motor controller circuit and not a lighting product. Ivey describes using a combination of series/parallel thermal switches to activate a ventilation fan when a given temperature is reached within a combination ventilation fan-light assembly. Ivey does not disclose a trim assembly for use in connection with a recessed lighting housing.